FR2467488A1 - THREE-WAY MICROWAVE COMBINATOR / DIVIDER DEVICE ADAPTED FOR EXTERNAL ISOLATION RESISTORS - Google Patents

Abstract

The invention relates to a three-way microwave combiner / divider device suitable for external insulation resistors. This device comprises a common input port 11, three output ports 12, 13, 14 and two isolation ports 15, 16 interconnected by quarter-wave transmission line sections 19, 23, 29, 24 , 28 or three-quarter wave 20, 21, 22, 25, 26, 27. The assembly is preferably made in microstrip. The invention applies in particular to the combination of the output signals of three microwave sources. (CF DRAWING IN BOPI)

Description

The present invention generally relates to devices

  power combiners / dividers in the field of microwaves,

  especially for transmission and reception systems in this field.

  In the prior art, the combiner / divisor function is realized using conventional and well known means, among which is the hybrid ring coupler, the branch coupler, the in-line divider, the T-combiner / divider and the combiner /

  Wilkinson divider. The online configuration and the T configuration do not allow

  both resist isolation resistance. As a result, there is no possibility with them of maintaining a reasonable impedance matching if one of the sources whose powers are

  combined is faulty. In this context, when it comes to

  In cases where several power sources in the microwave field are realized with semiconductors and must have their outputs combined to obtain an increased transmissible power, the continuous operability can be very great. For example, such an arrangement may be used in an unserved or under-serviced station. Although possessing a long life by nature, microwave power generators built with semiconductors are generally able to provide only moderate power. Also, it is necessary to combine the output of several of these generators to obtain at the output a sufficient total power. The configurations of the combiners / dividers in line and in T are excluded for these applications, because of the absence of functional aptitude in case of failure of one

sources.

  The branch and hybrid ring configurations both have appropriate isolation resistances, and thus allow the isolation of a source in the event of a source failure, at least in part. However, none of them allows division by

  three or the combination of three sources on one output.

  In addition, the Wilkinson circuit has both isolation resistances and the possibility of division and multiple combinations. However, insulation resistors must be mounted internally. The result of this integration of the resistances in the band structure is that, if these resistances have a large dissipation in order to correspond to the nominal RF power, then an excessive parasitic capacitance is introduced, so that the losses

  resulting insertion are prohibitive.

  The present invention overcomes the disadvantages and limitations of the prior art by providing a novel solution to the problem of three-way and three-way combining in a way that

  will appear in this description.

  The invention provides a modified form of hybrid ring coupler, using quarter-wave tuned elements distributed to obtain the appropriate phase balance between the different signal paths. Unlike the known hybrid ring, additional line lengths are provided, so that there are three egress ports and common access or entry access, in addition to two isolation accesses. The device is from the reversible or reciprocal structural point of view: a signal at the input or common access port is distributed over three channels, and substantially one-third of the power appears on each of the three output ports. Associated line lengths between the various ports are adjusted so that the signals are in phase alignment at the exit ports and cancel at the access ports.

  isolation. As a result, shared energy appears in phases

in equal amplitudes.

  In the case of use in a combiner, three microwave phase-to-phase signals having the same amplitude are, by hypothesis, applied to the three output ports, these signals being added, in phase concordance, to the input access or common access and canceling access to isolation. The result is an effective combination, with common access, of the received signals. The invention will be better understood and other features

  will appear with the following description and accompanying drawings

  o: - Figure I.a shows a hybrid ring coupler according to the prior art; - Figure 1.b shows a branch coupler also known in the prior art;

  FIG. 1.c represents the so-called online configuration of a combination of

  nator / divider also known in the prior art; - Figure 1.d shows the T configuration according to the prior art;

  - Figure I.e represents the so-called Wilkinson circuit in its confi-

  known guration; FIG. 2 diagrammatically represents a three-way combiner / divider according to the invention; FIG. 3 represents an exemplary printed circuit embodiment (microstrip) of a three-way combiner / divider according to the invention; FIG. 4.a is a Smith chart of the standing voltage wave ratio existing at the common access of an exemplary embodiment of the invention constructed according to FIG. 3; FIGS. 4b, 4.c and 4.d are Smith charts describing the stationary voltage bandwidth of accesses 1, 2 and 3 of FIG. 3; and FIG. 5 represents a selected group of measured operating characteristics for an exemplary embodiment of the invention.

corresponding to Figure 3.

  As indicated in the foregoing, Figs. 1a through 1e are presented to illustrate the technological background, as they describe configurations known in the prior art. Some of the disadvantages and limitations of each of these devices of art

  have been presented above, concerning the prior art

  pool. Those skilled in the art will recognize each of these known devices

  which need not be described in detail.

  As for Figure 2, it schematically represents a

  three-way combiner / divider according to the present invention. The inventors

  This arrangement can be performed in accordance with an arrangement reproducing what is shown in FIG. 2. However, the configuration of FIG. 3, which is physically more convenient, is preferable for most applications.

  In the description of Figure 2 and, on the same subject,

  3, it will be assumed that the device is used as a power divider, but it is understood that it is perfectly reversible or reciprocal, and therefore able to combine signals applied to the outputs (branches) to provide a signal having a amplitude equal to the sum of the amplitudes of the signals applied to the three output ports, minus

  a minimum value of inherent losses.

  In Figure 2, the input port It will be considered as the power input, directly connected to the junction 11a. The point It will be called "common access" (common entry). The three output junctions or branches are respectively identified by the references 12a,

  13a and 14a. The respective output ports are 12, 13 and 14. The difference

  The difference between "access" and "junctions", according to the terminology adopted, is the length of printed conductor required to reach the edge of the substrate. In the embodiment according to Figure 3, it has been considered desirable that all outputs (branches) are

  located on the same side of the substrate.

  Continuing the description of Figure 2, the assembly 10

  schematically shown can be implemented on any material for transmission line, among several possible. For example, the strip line, microstrip, coaxial line, or even hollow waveguide could be used, although the

  The last city was then very inconvenient and cumbersome.

  The input or common access mentioned above is represented in 11. It is directly connected, with impedance matching

  appropriate, at the entrance junction, or communlia access junction.

  Three transmission line sections, each being a quarter-wave section, depart from 11a, namely section 19 going to junction 12a corresponding to first output port 12, section 29 from junction 11a to junction 14a corresponding to the third output port 14, and the section 24, which connects the junction 11a to the junction 13a, corresponding to the second output port 13. A three-quarter wave transmission line, consisting of three quarter-wave quarter sections. series, namely 20, 21 and 22, connects the junction 12a to the junction 15a. As

  as can be seen, the junction 15a corresponds to the isolation access 15.

  Similarly, a three-quarter-wavelength line, including quarter-wave sections 25, 26, and 27, extends from junction 13a to

  junction 16a, the latter corresponding to the second iso-

  16. Two additional quarter-wave sections 23 and 28 are

  junction 14a at junctions 15a and 16a, respectively. Resist

  external isolation circuits 17 and 18 are respectively connected to

  Isolation Access 15 and 16. As noted above, the effects of

  inherent citities, introduced by the relatively large dissipated power resistors 17 and 18, have substantially no effect in the circuit of FIG. 2, unlike the configurations of FIG.

the prior art. -

  In FIG. 3, reference 10a as a whole designates a more practical embodiment of the circuit of FIG. 2, of microstrip material. The microstrips are in fact printed circuit conductors supported by a substrate 45 of known type. The junctions 11a, 12a, 13a, 14a, 15a and 16a are shown in Figure 2 and Figure 3 for clarity. The quarter-wave sections 33, 34, 35 and 36 in FIG. 3 are respectively equivalent to sections 19, 23, 24 and 28 of FIG. 2. The three quarter-wavelength portion, comprising sections 20, 21 and 22 FIG. 2 is shown at 30 in FIG. 3. Similarly, the section 31 in FIG. 3 is equivalent to the series sections 25, 26 and 27 shown in FIG.

in Figure 2.

  In FIG. 3, the printed conductors comprising the transmission line sections have a configuration compressed in the normal dimension direction to the length of the oblong substrate 45, in order to benefit from a reduced bulk. The three-quarter-wave sections 30 and 31, however, have, between their connected junctions, the same length as the equivalent transmission line sections in the case of FIG. 2. Similarly, the quarter section

  29a, corresponding to 29 in FIG. 2, is folded as shown in FIG.

  Figure 3, essentially with the same adaptation purposes

geometric.

  To be compatible with the input and output impedances of Figure 3, the input impedance of the common access (common input) It is assumed by 50 a. As a result, the conductor 46 is described as being a 50 n section with gradual or discontinuous transition to about 62.5 n in the portion 47, to accommodate the junction 11a. The folded quarter-wave section 29a is printed with a characteristic impedance of about 86Ω, and the quarter sections

  33, 34, 35 and 36 are printed with a characteristic impedance

  70.7 Q. About the impedance of a printed circuit line

  microband material, it is recalled that it is the width of the

  printed circuit which determines this impedance in a manner well known to those skilled in the art. In general, the larger lines, such as those shown in Figure 3, are those with a lower characteristic impedance than is the case with the longer lines.

narrow.

  From the foregoing, it follows that the impedances presented in 11a, 12a, 13a, 14a, 15a and 16a are all substantially 50 Q2, in agreement with the initial assumptions, and that the output leads 41, 42 and 43 are 50 Q sections, of equal length, so that no phase disparity is introduced between the accesses of

exit 12, 13 and 14.

  Adapters or compensating nipples 37, 38, 39, 40 and 44

  are represented, it being understood that these adapters may be necessary

  whether or not according to the construction accuracy of the device. Their role is to compensate for small errors in section length

of transmission line.

  Of course, in the microstrip material, the insulating substrate 45 has, on the back side (below) a ground conducting plane, according to the well-known microstrip construction technique. Typical materials for forming the insulating substrate include Teflon (Trade Mark) with fiberglass, and alumina. Such substrate materials have low loss angles and are easily fabricated to provide a uniform dielectric constant. The printed conductors shown in FIG. 3 may be copper strips, unless the substrate material is alumina, in which case gold is the most conductive material.

suitable.

  The quarter-wave and three-quarter-wavelength dimensions mentioned above relate to the wavelengths in the material,

rather than in the air or the void.

  A typical device, constructed as shown in Figure 3, operates in the range of 1.2 to 1.4 GHz, with a maximum power of the order of one kilowatt. However, a microband embodiment can be up to twenty-five kilowatts, provided that the "band / connector" interface

  be of appropriate design. Resistances 17 and 18 with relative dissipation

  can be easily chosen to maintain their characteristics over time. In other words, they can assume powers greater than those actually requested which increases the overall reliability and reduces the probability of failure. In the folded belt configuration according to Fig. 3, the dimension 32 need not be equal, and in fact it is obviously less than a quarter of a wavelength, although the total lengths of the sections 30 and 31 are each of

three quarters of wavelength.

  As already indicated, other kinds of material for transmission lines could be used to make the device according to the invention. Although the microband is the preferred material,

  provided that the power levels do not exceed approximately twenty-

  five kilowatts maximum, the stripline, in which the conductors are sandwiched between two parallel ground planes,

  is probably the second most suitable material.

  In Figures 4.a, 4.b, 4.c and 4.d, Smith charts describe typical steady-state voltage waveband readings measured for three frequencies (1,2, 1,3 and 1, 4 OHz) for the common access (input 11), the output port 12, the output port 13 and the port 14, respectively. These values apply to the configuration

according to Figure 3.

  In FIG. 5, the values of the couplings with respect to the input access (common input) are represented for the three accesses

  Release. Couplings between output ports are also represented

  12 access 12, access 12 access 14 and access 13 access 14. In addition, the isolation access couplings with respect to

common access are represented.

  With regard to the coupling of the output ports, the optimal theoretical value (zero loss) is determined by the formula 10 Log -, in which N is equal to 3, which corresponds to the three-way split. This theoretical value is 4.77 dB. However, due to unavoidable losses in a real device, the coupling values

  The real numbers shown in Figure 5 fall just below 5 dB.

  Other modifications and possible variants will be apparent to those skilled in the art who have taken cognizance of the principles of the present invention.

  invention. It is therefore understood that the examples in this description

  can not be considered as limiting the scope of

  the invention, these examples and description being presented as

in no way limiting.

Claims (7)

  1. Three-way microwave combiner / divider device having common access, first, second, and third branch ports, first and second isolation ports, common junction, first, second, and third ports junction, and a first and a second isolation junction, each connected to one of said corresponding ports, characterized in that it comprises: - first means comprising a first quarter-wave transmission line section, between said common junction and said first junction, a second quarter-wave transmission line section between said common junction and said second junction, and a third quarter-wave transmission line section between said common junction and said third junction; second means comprising a first section of three-quarter transmission line, from said first junction   at said first isolation junction, and a second section of -   three-quarter-wavelength transmission line, from said second junction to said second isolation junction; third means including a fourth quarter-wave transmission line section, from said third junction to said first isolation junction, and a fifth quarter-wave transmission line section, from said third junction to said third junction line; second isolation junction; and a first and a second external insulation resistance connected individually to said first and said second isolation access, respectively, and means respectively connecting said first and said second isolation access to said first isolation access; and second isolation junctions.   2. Device according to claim 1, characterized in that said three quarter wavelength sections are each composed of several quarter wave sections in series and are physically folded, to adapt to geometrical requirements, between said common access   and said branch and isolation ports.   3. Device according to claim 1, characterized in that said combiner / divider is made of microstrip, said first, second and third means comprising conductors printed on a insulating substrate.   4. Device according to claim 3, characterized in that said three-quarter transmission line sections each comprise a U-shaped conductive pattern of which two parallel legs are separated by a space not exceeding a quarter of a length. 'wave.   5. Device according to one of claims 3 or 4, characterized   characterized in that said transmission line sections of said first, second and third means are insulatively printed conductors in oblong configuration, said first and second transmission line sections being collinear with a first printed conductor line, said fourth and fourth transmission line sections being fifth sections of transmission lines being collinear along a second printed conductor line substantially parallel to said first line and said first and second printed conductor lines being separated laterally by a gap of less than a quarter of a wavelength, said third section of transmission being folded to offer a quarter-wave ride.   6. Device according to claim 5, characterized in that said three-quarter transmission line sections are each an oblong, U-shaped printed circuit line whose length is greater than a quarter of a wavelength. and whose width is substantially equal to said lateral space between said   first and second lines in printed conductor.   7. Device according to claim 6, characterized in that said first, second and third junctions each have an extension up to a corresponding access along the same edge of said substrate, these extensions forming meanders as necessary to obtain paths of equal length of each of said   junctions to a corresponding access.